feat: secure trade with other players - wire, RuntimeTradeState, the

authored gmSecureTradeUI window, and both retail open paths

Three-lane research first (docs/research/2026-08-14-trade-lane{A,B,C}):
retail gmSecureTradeUI decode, the byte-exact ACE/decomp/holtburger
three-way wire agreement, and the acdream seam map (which found both
open paths ALREADY classified by the ported policy - OpenSecureTrade on
Use-a-player, StartSecureTrade on drag-item-onto-player with the
DragItemOnPlayerOpensSecureTrade option - dead-ending at a stub toast).

- Core.Net: TradeRequests builders (0x1F6-0x204, retail's CM_Trade
  senders byte-checked against ACE's readers; the ACE-discarded
  AcceptTrade echo carries zero-count item lists - AD-94), corrected +
  completed inbound parsers (0x1FD-0x208; the old AddToTrade parser
  missed the SIDE dword, TradeFailure missed the reason), delegate-hole
  registrars, six WorldSession sends. 10 golden-byte tests.
- Runtime: RuntimeTradeState, the third sibling J-owner (fellowship/
  allegiance shape): session-scoped, clears at generation reset (new
  stage Trade=14), staged teardown stage 11 (Identity/EntityObjects
  shift 12/13, TeardownStageCount 14 - the FA2-era per-stage-flag test
  caught the mapping exactly as designed), combined ownership ledger,
  event routing with ACE's wrong-initiator RegisterTrade landmine
  honored (partner = whichever guid is not mine). 7 conformance tests.
- App: SecureTradeUiController binds the dedicated authored LayoutDesc
  0x2100000D (root 0x1000007A - gmSecureTradeUI::PostInit's exact ids):
  partner name/status/count/grid, the authored 'Trade' accept toggle
  (accept <-> decline withdraw), 'Clear All' (ACE clears BOTH sides -
  surfaced honestly), the X close, drop-on-your-grid staging, per-mode
  accept cues (partner icon's authored Highlight state + Trade button
  Selected latch). Mounted via the vendor recipe (nine-slice chrome,
  hidden until RegisterTrade). ItemInteractionController's two policy
  arms now raise SecureTradeRequested instead of the stub toast; the
  drag path queues the dragged item until the window registers
  (ClientTradeSystem::AttemptToTradeItem @0x0056DF80's shape).

Register: AD-94 (accept-echo zero-count lists), AD-95 (numeric-only
count texts pending template verification).

Suites: App 4,990/3, Core.Net 905, Runtime 1,626 - all green. The
panel itself is user-gate acceptance (two-client connected trade), the
#372-class lesson: fixture-green alone is not acceptance for a mount.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/AcDream.App.Tests/UI/Layout/PowerbarLayoutProbeTests.cs

@@ -71,6 +71,38 @@ public sealed class PowerbarLayoutProbeTests
         }
     }
 
+    /// <summary>2026-08-14 trade research: locate the LayoutDesc that authors
+    /// gmSecureTradeUI's element tree (lane A gave element ids 0x10000085-8B
+    /// but not the layout id) and dump it.</summary>
+    [Fact]
+    public void ProbeSecureTradeLayout()
+    {
+        if (Environment.GetEnvironmentVariable("ACDREAM_PROBE_POWERBAR") != "1")
+            return;
+
+        var datDir = Environment.GetEnvironmentVariable("ACDREAM_DAT_DIR")
+            ?? Path.Combine(
+                Environment.GetFolderPath(Environment.SpecialFolder.UserProfile),
+                "Documents",
+                "Asheron's Call");
+        using var dats = new DatCollection(datDir, DatAccessType.Read);
+        var strings = new DatStringResolver(dats);
+
+        int scanned = 0;
+        for (uint layoutId = 0x21000000u; layoutId <= 0x210001FFu; layoutId++)
+        {
+            ElementInfo? root = LayoutImporter.ImportInfos(dats, layoutId);
+            if (root is null)
+                continue;
+            scanned++;
+            if (FindById(root, 0x10000088u) is null)
+                continue;
+            Console.WriteLine($"[pbprobe] SECURE TRADE LAYOUT = 0x{layoutId:X8}");
+            DumpElement(strings, root, 0);
+        }
+        Console.WriteLine($"[pbprobe] scanned {scanned} layouts");
+    }
+
     private static ElementInfo? FindById(ElementInfo element, uint id)
     {
         if (element.Id == id) return element;